12 BULLETIN 1201, U. S. DEPARTMENT OF AGRICULTURE. 
this table the results obtained by spraying the extracts of "cube," 
derris, and pyrethrum, and the nicotine sulphate upon Mocroziphvm 
sp. .1 are the same as recorded in Table 5. 
The extracts+soap+water (2, 1, and 1/2+2+100) of "cube," those 
of derris (2 and 1+2 + 100), and nicotine sulphate (l/400)+soap+ 
water (2.5+2+100) are equally toxic against Marrosiphum rosae 
(none over half grown); while pyrethrum extract (2+2+100), 
derris extract (1/2+2+100), and nicotine sulphate (1/800) are about 
equally toxic, but the pyrethrum extracts (1 and 1/2+2+100) were 
less toxic and were inefficient. 
The potato aphis (M. solan? fotii), living on the pubescent under- 
side of the leaves of a western jimson weed (Datura meteloides 
Dunal), were particularly difficult to kill. Nicotine sulphate (1/400) 
with soap (2+100) killed only 75 per cent of them within 24 hours, 
and nicotine sulphate (1/800) only 60 per cent; but when the soap 
was doubled. 95 per cent of the aphids were killed by each of the 
nicotine sulphate solutions. Theextracts+soap+water (4+4+KK)) 
of " cube," derris, and pyrethrum were found efficient against this 
aphis, but a "cube" extract (2+2+100) killed only 50 per cent of 
them within 24 hours. The most satisfactory mixtures tested on this 
aphis were kerosene emulsions containing the extracts. The ex- 
trarts+water (1+100) of "cube," derris, and pyrethrum+2.5 per 
cent of kerosene emulsion were about equally toxic and efficient ; 
while the pyrethrum extract (2+100), derris extract (1+100), and 
"cube" extracts (1 and 1/2+100), each +1.25 per cent kerosene 
emulsion, were efficient; but the pyrethrum extract (1 and 1/2+100), 
and derris extract (1/2+100), each +1.25 per cent of kerosene emul- 
sion, were inefficient. The extracts + soap + water (1+4+100) 
killed about 20 per cent of the aphids, while the control mixture 
containing 2.5 per cent of kerosene emulsion killed only 15 per cent 
of the aphids sprayed. This shows the effect of adding the extracts 
to the kerosene emulsion. 
Table 6 shows that these alcoholic extracts are very promising 
insecticides, although not all of the 11 species of aphids tested were 
easily killed by them. Regarding the minimum dosage required to 
produce efficient killing, which is here considered 90 per cent or more 
within 2f hours, it appears that "cube" extract is 12 times as toxic 
as pyrethrum extract and 3 times as toxic as derris extract. These 
differences in toxicity are partially explained by the fact that the 
concentration of the "cube" extract is 5.29 per cent, while the con- 
centrations of the derris and pyrethrum extracts, respectively, are 
2,89 per cent and 4.08 per cent. Relative to the following four insec- 
ticides used with soap (2 pounds to 100 gallons of water), the lowest 
concentrations found which produce efficient killing are: Pyrethrum 
exl i act from -J pounds of powder, derris extract from one-half pound, 
"cube" extract from one-sixth pound, and 40 per cent nicotine sul- 
phate (l/l.-JU') strength). 
\'<rrious extracts from "cube " against aphids. — Reference to Table 
7 shows the comparative results obtained by spraying five specie of 
aphids with various "cube" extracts. Practically no difference in 
toxicity between the cold and hot alcoholic extracts is shown. The 
resin wa.s inefficient in all tests, and consequently contains only a 
portion of the toxic principle present in this plant, but in the 
